全文获取类型
收费全文 | 35594篇 |
免费 | 75篇 |
国内免费 | 97篇 |
专业分类
系统科学 | 209篇 |
丛书文集 | 764篇 |
教育与普及 | 82篇 |
理论与方法论 | 236篇 |
现状及发展 | 15812篇 |
研究方法 | 1483篇 |
综合类 | 16700篇 |
自然研究 | 480篇 |
出版年
2013年 | 216篇 |
2012年 | 494篇 |
2011年 | 973篇 |
2010年 | 225篇 |
2008年 | 635篇 |
2007年 | 637篇 |
2006年 | 685篇 |
2005年 | 681篇 |
2004年 | 610篇 |
2003年 | 641篇 |
2002年 | 657篇 |
2001年 | 1057篇 |
2000年 | 996篇 |
1999年 | 646篇 |
1992年 | 632篇 |
1991年 | 505篇 |
1990年 | 527篇 |
1989年 | 527篇 |
1988年 | 526篇 |
1987年 | 538篇 |
1986年 | 530篇 |
1985年 | 673篇 |
1984年 | 534篇 |
1983年 | 452篇 |
1982年 | 400篇 |
1981年 | 387篇 |
1980年 | 499篇 |
1979年 | 1082篇 |
1978年 | 954篇 |
1977年 | 954篇 |
1976年 | 673篇 |
1975年 | 747篇 |
1974年 | 1042篇 |
1973年 | 880篇 |
1972年 | 888篇 |
1971年 | 1145篇 |
1970年 | 1501篇 |
1969年 | 1124篇 |
1968年 | 1047篇 |
1967年 | 1114篇 |
1966年 | 929篇 |
1965年 | 677篇 |
1964年 | 192篇 |
1959年 | 412篇 |
1958年 | 581篇 |
1957年 | 507篇 |
1956年 | 411篇 |
1955年 | 355篇 |
1954年 | 405篇 |
1948年 | 227篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Humoral immune reactions to heat shock proteins (hsp) from microorganisms are one aspect of microbial infections in humans. The production of antibodies which are specific to epitopes present on procaryotic hsp leads also to the appearance of cross-reactive serum antibodies in the host organism that react with human hsp. This article discusses the consequences of such autoreactive antibodies for the host in context with the development of immune tolerance and autoimmune diseases, especially rheumatoid arthritis (RA), and in experimental animal models for arthritis such as adjuvant arthritis in rats. On the basis of epitope cross-reactivity between hsp and other host proteins, a hypothesis is presented for the development of autoimmune disease following the production of hsp-specific antibodies. 相似文献
13.
M. Lazzari V. Franceschini G. Minelli F. Ciani 《Cellular and molecular life sciences : CMLS》1993,49(4):277-281
The corrosion cast technique provided for the first time an excellent three-dimensional visualization of the vascular pattern of the choroid and iris in the newt eye. The results show the presence of a single arterial afference to the choroidal and iris capillaries: the ophthalmic artery is the origin fo both ciliary arteries and the long posterior ciliary artery. Slightly behind the equatorial circumference of the eyeball the venous drainage consists of a single vessel on the dorsal side and two distinct vessels on the ventral one. It receives blood from both iris and choroid. The surface of the plastic endocasts shows some details of fine luminal structures of the endothelial cells. Shallow depressions may be regarded as imprints of endothelial cell nuclei, and they are distinctly different for arteries and capillaries. The angioarchitecture of the newt eye differs from that of brain in that hairpin-shaped capillary loops are not observed at all. 相似文献
14.
15.
R. Poggioli A. V. Vergoni A. Bertolini 《Cellular and molecular life sciences : CMLS》1985,41(2):265-266
Summary Hydrochlorothiazide, acutely injected in rats, has a weak analgesic activity per se and potentiates and prolongs the antinociceptive effect of morphine.This work was supported in part by grants from Consiglio Nazionale delle Ricerche, and by Ministero della Pubblica Istruzione, Roma. 相似文献
16.
17.
This paper assesses the information content of two survey indicators for consumption developments in the near future for eight European countries in the period 1985–1998. Empirical work on this topic typically focuses on consumer confidence, the perceptions of buyers of consumption goods. This paper examines whether perceptions of sellers of consumption goods, measured by retail trade surveys, may also improve short‐term monitoring of consumption. We find that both consumer confidence and retailer confidence embody valuable information, when analysed in isolation. For France, Italy and Spain we conclude that adding retail confidence does not improve the indicator model once consumer confidence has been included. For the UK the reverse case is obtained. For the remaining four countries we show that combining consumer sentiment and retail trade confidence into a composite indicator leads to optimal results. Our results suggest that incorporating information from retail trade surveys may offer significant benefits for the analysis of short‐term prospects of consumption. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
18.
S. J. Leybourne 《Journal of forecasting》1993,12(1):49-62
A linear regression model with random walk coefficients is extended to allow for linear restrictions between the coefficients to be satisfied at each point in time. Estimation in this model is shown to be no more involved than estimation in the standard model. It is also demonstrated how, after a slight modification to the testing problem, classical test procedures may be applied to the problem of testing for such restrictions. The performance of the Lagrange Multiplier test for a variety of different restrictions is then investigated via simulation. An empirical application involving testing for homogeneity in a random walk coefficient version of the AIDS model is given. 相似文献
19.
Growth hormone signal transduction 总被引:1,自引:0,他引:1
Growth hormone (GH) promotes animal growth by stimulating bone and cartilage cell proliferation, and influences carbohydrate and lipid metabolism. Some of these effects are brought about indirectly via somatomedin induction in hepatocytes, others by acting directly on the target cells. In either case, GH first binds to specific receptors on cells to trigger a sequence of biochemical events culminating in a biological response. Recently much has been learnt about the molecular structure of GH receptor, its binding to ligand, and the ensuing signal transduction events. 相似文献
20.
We recently reported on a linkage study within a Quarter Horse lineage segregating hyperkalaemic periodic paralysis (HYPP), an autosomal dominant condition showing potassium-induced attacks of skeletal muscle paralysis. HYPP co-segregated with the equine adult skeletal muscle sodium channel alpha subunit gene, the same gene that causes human HYPP. We now describe the Phe to Leu mutation in transmembrane domain IVS3 which courses the horse disease. This represents the first application of molecular genetics to an important horse disease, and the data will provide an opportunity for control or eradication of this condition. 相似文献